Recent questions in Class12

Resonance frequency of a circuit is f. If capacitance is made 4 time the initial value, the resonance frequency will be

asked Mar 27, 2014 by meena.p

1 answer

Voltage and current in the a.c circuit are given by $V= 5 \sin (100 \pi t -\large\frac{\pi}{6})$ and $I= 4 \sin (100 \pi t + \pi/6)$

asked Mar 27, 2014 by meena.p

1 answer

In an LCR series circuit, connected to a source E is at resonance then

asked Mar 27, 2014 by meena.p

1 answer

Two coaxial solenoids are made by winding their insulated wire over a pipe of cross sectional area $A= 10\;cm^2$ length $20\;cm$ .One of the solenoids has 200 turns and another 400 turns. the mutual inductance is .

asked Mar 27, 2014 by meena.p

1 answer

Two induction coil of inductance $L_1$ and $L_2$ are separated by a considerable distance. On connectivity them in series the equivalent inductance is

asked Mar 27, 2014 by meena.p

1 answer

A current carrying square loop is placed near an infinitely long current carrying wire. The torque acting on the loop is

asked Mar 27, 2014 by meena.p

1 answer

A current caring wire AB is placed near another long current carrying wire CD. If free to move AB will have D.

asked Mar 27, 2014 by meena.p

1 answer

A circular loop of radius R, carrying current I lies in $X-Y$ plane with its centre at origin. The total magnetic flux through $X-Y$ plane is

asked Mar 27, 2014 by meena.p

1 answer

When a wire loop is rotated in a magnetic field, the direction of induced emf

asked Mar 26, 2014 by meena.p

1 answer

A magnet is dropped inside a long hollow vertical metal pipe. During the fall the acceleration of magnet.

asked Mar 26, 2014 by meena.p

1 answer

The current flowing in two coaxial coils is in the same direction. If we increase the distance between the two , the electric current will,

asked Mar 26, 2014 by meena.p

1 answer

An LCR circuit given below is connected to a variable frequency w and constant peak voltage $V_0$ . at certain $w_0=w_1$ the rms voltage value across L, C and R are respectively $100\;V,60\;V$ and $30\;V$ . At different value of $w_0=w_2$ we find the voltage across resistance is $50\;V$ Then $w_2$ is

asked Mar 26, 2014 by meena.p

1 answer

The $220\;v$ input is supplied to a transformer . The output circuit draws current of $2.0\;A$ at $440\;V$ If efficiency of transforms is $80\%$ te current drawn by primary circuit is

asked Mar 26, 2014 by meena.p

1 answer

The Voltage time (V-t) graph of triangular wave having peak value $V_0$ is shown. The rms value of V in interval $t=0$ to $t=\large\frac{\pi}{4}$ is

asked Mar 26, 2014 by meena.p

1 answer

A conducting ring of radius R is placed in a magnetic field perpendicular to the plane of the coil at the rate of $\beta$ . Then Which one is correct ?

asked Mar 26, 2014 by meena.p

1 answer

A thin semicircular ring of radius 'a' is falling with its plane vertical to a horizontal magnetic field induction $\overrightarrow {B}$ .At the given position PQR the speed of ring is 'v' , the potential difference developed across the ring.

asked Mar 26, 2014 by meena.p

1 answer

Power loss in AC circuit will be minimum when

asked Mar 26, 2014 by meena.p

1 answer

A fully charge capacitor of capacity $0.1\; \mu F$ is discharged through a resistor of resistance $10^6$ ohms. The time in which the potential falls to half its original value is $[\log_e2=0.6931]$

asked Mar 25, 2014 by meena.p

1 answer

A coil of inductance $L= 150\;mH$ and resistance $R= 70\;m \Omega$ is connected to a voltage source. How soon will the voltage attain $50\%$ of initial value

asked Mar 25, 2014 by meena.p

1 answer

A conducting rod of length $l=2\;cm$ moves with velocity 12 m/s at an angle $30^{\circ}$ to a magnetic field produced between two square faced poles of side 2 cm. If flux leaving the face is $5 \mu Wb$ the induces emf is

asked Mar 25, 2014 by meena.p

1 answer

A 1200 turn coil of mean area $500 \;cm^2$ is held perpendicular to a uniform field of $4 \times 10^{-4}$ tesla. The resistance of coil is $20 \Omega$ . What will be the average induced current when coil turns through $180^{\circ}$ in $0.1\;$ second?

asked Mar 25, 2014 by meena.p

1 answer

Effective value of current is $5.0\;amp$ in a 50 cycle ac circuit. What is value of current $\large\frac{1}{300}\;$ seconds after it is zero ?

asked Mar 25, 2014 by meena.p

1 answer

An LCR circuit has $L= 3.0 H, C= 27 \;\mu F$ and $R= 7.4 \;\Omega$ with a certain a factor. To improve the sharpness of resonance by reducing its full width at half maximum by a factor of 2, with out changing $w_0$ , we can

asked Mar 25, 2014 by meena.p

1 answer

In an ac circuit with combination of L and C which one of following represents the variation of frequency f with reactance X?

asked Mar 25, 2014 by meena.p

1 answer

The equation of AC voltage is $E=220\; \sin (wt+\large\frac{\pi}{6})$ and AC current is $I= 10 \sin (wt+\large\frac{\pi}{6})$ The average power dissipated is

asked Mar 25, 2014 by meena.p

1 answer

A bulb is rated $100\;V,100\;W$ The inductance of an inductor that should be connected in series with the bulb to operate the bulb at rated power, with ac source $200 V, 50 \;Hz$

asked Mar 25, 2014 by meena.p

1 answer

An AC Source gives a voltage of $V= 20\; \cos \;(2000 \;t)$ . It is connected in a circuit as shown. The voltmeter reading is

asked Mar 25, 2014 by meena.p

1 answer

In the given circuit what will be reading of voltmeter.

asked Mar 25, 2014 by meena.p

1 answer

For the series LCR circuit what is resonance frequency and amplitude.

asked Mar 25, 2014 by meena.p

1 answer

A LC circuit has a $10\;V,50\;Hz$ AC sources, A current of $1A$ flows in the circuit. The voltage leads by u phase angle of $\large\frac{\pi}{3}$ radians. The Value of resistance and inductive resistance are

asked Mar 25, 2014 by meena.p

1 answer

A fully charge capacitor C either initial charge q is connected to a coil of self inductance. L at $t=0$ the time at which the energy is stored equally between electric and magnetic field is

asked Mar 24, 2014 by meena.p

1 answer

A metal rod of resistance $20 \;\Omega$ is fixed along the diameter of a conducting ring of radius $0.1 m$ . A magnetic field of $B=50T$ acts perpendicular to the plane The ring rotates with an angular velocity of $w=20\;rad/s$ about its axis . An external resistance of $10 \;\Omega$ is connected across center and rim of the ring. What is current through the external resistance.

asked Mar 24, 2014 by meena.p

1 answer

In the circuit given the switch is closed at time $t=0$ What is the amount of charge passing through the battery in are time constant ?

asked Mar 24, 2014 by meena.p

1 answer

In the given circuit shown : $L= 200\;mH;$ Emp of battery $E= 12 V$ $R_1=R_2=2 \Omega$ the internal resistance of battrey is negligible . The potential drop across the inductance L after time t.

asked Mar 24, 2014 by meena.p

1 answer

A plane Electro magnetic wave of frequency $30\; MHZ$ travels in free space component of wave at a point $E= 6V/m$ along y direction . The magnetic field component B at this point would be

asked Mar 24, 2014 by meena.p

1 answer

A emf of 10V is applied in a circuit containing inductance L and resistance R. $L=5H$ and $R= 10 \;\Omega$ . The ratio of current at $t =\infty$ and $t= 1\;s$ in

asked Mar 24, 2014 by meena.p

1 answer

A coil of inductance $84\;mH$ and resistance $8 \Omega$ is connected to $12 V$ battery. The current in the coil is 1 A at approximately

asked Mar 24, 2014 by meena.p

1 answer

A uniformly would soleacidal (ie) of self inductance $8 \times 10^{-4}\;H$ and resistance $45\;L$ is broken into two identical coils. These colis are then connected in parallel across a battery of $10V$ of negligible resistance the time constant for this circuit is

asked Mar 24, 2014 by meena.p

1 answer

A inductor $(L= 50 \;mH)$ and resistor of $R =100\;\Omega$ and a battery , of emf 100 V is initially connected in series. Then the battery is short circuited , the current flowing 1 ms after the short circuit is

asked Mar 21, 2014 by meena.p

1 answer

A conducting circular loop is placed in a uniform field of $B=0.05\;T$ with its plane perpendicular to the loop. The radius of loop is made to shrink at constant rate of $0.5\;mm$ per second. The induced emf when radius is $2 \;cm$ is

asked Mar 21, 2014 by meena.p

1 answer

A current $I= 10 \sin (100 \pi t)$ ampere is passed in first coil which induces a maximum emf of $5 \pi$ volts in second coil. The mutual inductance M is

asked Mar 21, 2014 by meena.p

1 answer

A circular coil of radius $30\; cm$ and resistance $\pi^{2}\;Ohms$ is rotating in a uniform magnetic field $B=10^{-2}$ . Axis of rotation is diameter of coil which is perpendicular to direction of B. If Coil rotates with $200\;rpm$ the current induced in coil is

asked Mar 21, 2014 by meena.p

1 answer

A conducting rod AB of length 1 m is moving with uniform speed of $2\;m/s$ in a uniform magnetic field of 4T which is directed perpendicular to the plane of motion of the rod AB. A capacitor of capacity $C= 10\;\mu F$ is connected. The charge on the capacitor is

asked Mar 21, 2014 by meena.p

1 answer

A horizontal wire AB of length l is free to slide on a vertical conducting frame as shown. The wire has mass m and length l and resistance of circuit is R. The system is placed in a uniform magnetic field B directed perpendicular to the frame. The wire after falling a distance under the influence of gravity aquires a terminal speed equal to

asked Mar 21, 2014 by meena.p

1 answer

A conducting circular loop of radius a and resistance R is kept in a horizontal plane. A vertical time varying magnetic field $B=2t$ is switched on at $t=0$ Then the flow of charge per unit time from any section of coil is

asked Mar 21, 2014 by meena.p

1 answer

A magnetic flux passing perpendicular to plane of a coil is varying according to the relation. $\phi =3t^2+2t+5$ milliwebers. the emf induced at $t=2 \;sec$ is :

asked Mar 21, 2014 by meena.p

1 answer

An aeroplane in which the distance between the tips of using is $50\;m$ is flying horizontally with speed of $360\;km/hr$ over a place where the vertical component of earth's magnetic field is $2.0 \times 10^{-4}\;Weber /m^{2}$ The potential difference between the tips of wings will be

asked Mar 21, 2014 by meena.p

1 answer

In the experiment to find the value of unknown resistance using meter brige the circuit is as shown below . under the condition that the galavanometer shows null deflection value of R is :

asked Mar 20, 2014 by meena.p

1 answer

Which of the following figures represents an integrated circuit?

asked Mar 20, 2014 by meena.p

1 answer

The type of graph between length of a simple pendulum and time period is

asked Mar 20, 2014 by meena.p

1 answer

Ask Questions, Get Answers